When producing, removing or recovering crystallizable compounds from aqueous solutions, often the problem of scale deposition in the equipment occurs.
Scale deposition is a phenomenon that can occur in all kinds of processes. It is an unwanted occurrence that causes a number of operational problems such as plugging of equipment, inefficient usage of chemicals, increased utility costs, lost production due to downtime, corrosion, and downgraded products from increased dirt counts.
Scale deposits that have been identified include complexes of calcium (carbonate, oxalate, sulfate, silicates), aluminum (silicates, hydroxides, phosphates), barium, such as barium sulfate, iron, such as hydroxides, and magnesium, such as sulphates or silicates.
An example of a process wherein scale deposition is a problem is the reverse osmosis of water to produce purified water. In case the water to be treated contains amounts of scale forming components, in due time the reverse osmosis membrane gets clogged by scale and becomes damaged. Accordingly, the equipment has to be taken out of production in order to remove the scale. This has a negative influence on the economics of the process.